Climate change enhances methane emissions from freshwaters

It's a vicious circle: Due to climate change, including rising temperatures, more and more methane is bubbling up from freshwaters around the world.

The release of the greenhouse gas methane again leads to a further increase in temperature and an acceleration of climate change. Scientists from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) were involved in a Dutch study showing a clear correlation between temperature rise and methane emissions from water bodies. A temperature rise of one degree Celsius leads to six to 20 percent higher methane emissions.

Shallow
lakes, ponds, rivers and wetlands are responsible for a large
proportion of global natural greenhouse gas emissions, making them
particularly relevant to climate impact research. Most of the methane is
caused by bubbles filled with methane gas that develop in the sediment
at the bottom of these water bodies. As soon as the bubbles reach the
water surface, the greenhouse gas enters the atmosphere.

For the study, an international team of scientists evaluated data on
methane release from diverse waters around the globe – ranging from
local fishponds to postglacial lakes in Scandinavia to subtropical city
ponds in China. In addition, the influence of rising temperature on
methane release was measured in a laboratory study at the Dutch
Institute of Ecology (NIOO-KNAW).

Higher temperatures, more methane – more methane, higher temperatures

In eight large tanks filled with water and sediment, the researchers
mimicked the waters and environmental conditions of our latitudes over a
period of one year. A simulated temperature increase of 4°C resulted in
51 percent higher methane emissions from released gas bubbles
throughout the year. "The temperature effect on methane release was
primarily due to increased microbial activity in the sediment," explains
Dr. Sabine Hilt,
co-author of the study and working group leader at the IGB. The
scientists have calculated that a temperature rise of only 1°C would
lead to six to 20 percent higher emissions of methane bubbles, which in
turn would result in an additional increase in temperature.

"Every tonne of greenhouse gas that we emit leads to additional
emissions from natural sources such as methane bubbles,” reminds Prof.
Dr. Sarian Kosten, head of the study and former IGB guest scientist.
"Luckily, the opposite is also true: if we emit less greenhouse gas and
the temperature drops, the methane emissions from natural sources drop,
too.” Measurements in different water types and climate zones worldwide
could provide more accurate predictions for future methane emissions
– an important premise for forecasts of global warming trends and to
counteract.